This invention relates to sprockets for chain saws and more particularly, to a chain saw sprocket that incorporates wear mark indicators to alert the chain saw user to the appropriate time for sprocket replacement.
Heretofore, chain saw sprockets have included no clear means to determine the end of their useful service life. Accordingly, chain saw users have been unsure as to when to replace the chain saw sprocket for optimum service and performance of their machine.
A chain saw sprocket is typically driven by a clutch drum and includes saw chain driving teeth which engage the drive links of a saw chain, thereby to drive the latter around a guide bar. Chain saw sprockets are generally of two types. One type is the spur or open sprocket type wherein a plurality of radially extending teeth are positioned to engage the driving tangs of the saw chain drive links. The other type is known as a rim sprocket. This generally comprises a pair of disc-shaped cylindrical elements or rings having a plurality of pockets formed therebetween which receive the depending drive tangs of the saw chain drive links. A plurality of wedge-shaped teeth are positioned between the rims. The drive tang of a drive link is received in each of the pockets as the sprocket is rotated under power. The undersides of the side links or side plates of the saw chain ride on the rims. Rim sprockets give smoother chain operation and result in less wear and chain damage because the chain is supported on the circular rims.
As a saw chain rides on each of the types of sprockets, wear occurs to the sprocket. Heretofore, there has been no means to indicate to the chain saw user when the sprocket should be replaced.
It is thus the principal object of the present invention to provide a chain saw sprocket with wear mark indicators to let the chain saw user know when the sprocket should be replaced.
A further object of the present invention is to provide such a wear mark indicator in the form of a groove of a selected depth in an area of each sprocket which will be contacted either by the drive tangs of the drive links or by the side links or plates and which groove is positioned to be readily visible to the user.